Extension ladders, combination ladders, and stepladders consist essentially of two rails with rungs between the rails. Various accessories, for example levelers, wheels, tool or paint can hooks and plank support brackets, can be attached to the ladders to help one work from the ladder. Each of these accessories typically has its own method of attachment to the ladder, for example releasably hooking onto the rungs or securely held to the rails by bolts placed through holes specially drilled into the rails and threaded into a nut or receptacle of the accessory.
For example, for many types of ladders it is useful to have a leveler at the bottom of one leg or both legs. The leveler effectively adjusts the length of the bottom of the leg so that the ladder will go straight up from uneven ground or from different treads in a staircase. For safety, levelers are preferably securely bolted to the rails of the ladder or a static portion of the leveler may be integral with the leg of the ladder.
For ladders that are often used without an accessory, it is undesirable to have the extra weight of the accessory always present. Although accessories have been designed that quickly attach to rungs of a ladder or slip over the bottoms of the rails to achieve a quick attachment and release feature, these attachments are not sufficiently secure and include protrusions that catch on objects, damaging the object or the protrusion or creating a hazard.